In busy downtown San Francisco, the simultaneous historic renovation of the oldest athletic club in the nation along with its new, 10-story sister facility made this project a huge task, with extensive excavation, construction challenges, and careful seismic modernization.
- The renovation of the historic 1910, brick masonry structure included accommodating 18 new hotel rooms and other programming. The upper two floors were completely removed and replaced, while maintaining the existing outer historic masonry walls. Among many structural improvements, the project team modernized the interior including the pool with its signature, majestic skylights.
- The new, 10-story sister facility contains a swimming pool with movable bottom, locker rooms, a gymnasium, and seven levels of parking (one below grade). The building extends 70 feet below and 90 feet above grade. Working in a very tight, urban site with adjacent buildings on 3 property lines, the structure required complex underpinning and shoring of the adjacent structures and soil during excavation and construction.
- Forell/Elsesser provided prompt guidance when faced with multiple unforeseen conditions, allowing the project to stay on schedule with minimized costs. When existing foundations of the historic building were uncovered, several deviations from the original plans were present, requiring fast design revisions. Then, just two months before the publicized grand opening, severely corroded reinforcement was uncovered demanding extensive exploration and repair that the project team designed and implemented in a tight time frame.
As the Prime Consultant for the largest base isolation retrofit project in its time, Forell/Elsesser developed and implemented an unprecedented base isolation retrofit solution, directed 13 sub-consultants, and coordinated planning and sequencing of the retrofit construction of one of San Francisco’s greatest treasures.
- Built in 1912, the 550,000 s.f., 4-story City Hall building sustained damage from the 1989 Loma Prieta earthquake, necessitating repairs and a seismic retrofit. Base isolation was selected as the best solution because it is the most cost-effective solution and it allows for minimum intrusion to the ornate historic building, all while providing maximum seismic protection.
- In addition to base isolation, the project included installation of concrete shear walls around the light courts, and steel bracing at the dome/drum level.
- Forell/Elsesser assisted the City with obtaining funding for this project, and facilitated the extensive review process from federal, state, and local agencies.
- The large scale and breadth of this retrofit and repair project required careful planning and sequencing during construction to avoid damage to the precious historic fabric of the building and to avoid structural instability in the event of an earthquake during construction.
The LEED Gold Certified rehabilitation of this 1927 historic landmark included cost-effective seismic isolation, modernization of plumbing and electrical systems, and the addition of a new building with a connecting underground tunnel, all without altering the building’s historic integrity.
- The City of Pasadena had two primary goals for the seismic upgrade of their City Hall: to limit the intrusion of the new seismic upgrade into the significant historic elements of the building and to minimize the amount of damage anticipated after a major earthquake. To address both needs, friction pendulum isolators were placed between the foundation and basement. They were positioned on an off-grid system with one isolator in the center of four columns, thus supporting the entire square rather than one isolator per column. This innovative technique both minimized costs and increased construction efficiency.
- Forell/Elsesser benchmarked performance analysis against data obtained from the Northridge earthquake, showing that much of the historic non-structural elements were sound and did not require repair, thus keeping costs down.
- Shear walls were installed on the East end of the building’s wings, and a replacement of the deteriorating arcade with a utility tunnel running underneath, structurally tied the building’s two wings together. The project also included the modernization of Mechanical, Electrical and Plumbing systems, necessitating the redesign of structural systems to accommodate the new weight and space requirements of these energy-efficient additions.